This study is directed toward determining mechanisms important to the development and function of humoral and cellular immune responses; the nature of defficiency in immune function; and developing approaches to prophylaxis and/or therapy of infections and neoplastic disease associated with immune processes. BIBLIOGRAPHIC REFERENCES: Blaese, R.M.: Macrophage function in the development of immunocompetence and in immunodeficiency. J. Res. 20:67, 1976. Muchmore, A.V., and Blaese, R.M.: Immunoregulatory properties of fractions from human pregnancy urine: Evidence that HCG is not responsible. J. Immunology 118:881-886, 1977.